1. Field of the Invention
The present invention relates generally to improvements in automatic laser scanning bar code symbol reading systems, wherein laser scanning and bar code symbol reading operations are automatically initiated in response to the automatic detection of objects and/or bar code symbols present thereon.
2. Brief Description of the Prior Art
Bar code symbols have become widely used in many environments such as, for example, point-of-sale (POS) stations in retail stores and supermarkets, inventory management document tracking, and diverse data control applications. To meet the growing demands of this technological innovation, bar code symbol readers of various types have been developed for sending bar code symbols and producing symbol character data for use as input in automated data processing systems.
In general, prior art hand-held bar code symbol readers using laser scanning mechanisms can be classified into two major categories.
The first category of hand-held laser-based bar code symbol readers includes lightweight hand-held laser scanners having manually-activated trigger mechanisms for initiating laser scanning and bar code symbol reading operations. The user positions the hand-held laser scanner at a specified distance from the object bearing the bar code symbol, manually activates the scanner to initiate reading, and then moves the scanner over other objects bearing bar code symbols to be read. Prior art bar code symbol readers illustrative of this first category are disclosed in U.S. Pat. Nos. 4,575,625; 4,845,349; 4,825,057; 4,903,848; 5,107,100; 5,080,456; 5,047,617; 4,387,297; 4,806,742; 5,021,641; 5,468,949; 5,180,904; 5,206,492; 4,593,186; 5,247,162; 4,897,532; 5,250,792; 5,047,617; 4,835,374; 5,017,765; 5,600,121; 5,149,950; and 4,409,470.
The second category of hand-held laser-based bar code symbol readers includes lightweight hand-held laser scanners having automatically-activated (i.e. triggerless) mechanisms for initiating laser scanning and bar code symbol reading operations. The user positions the hand-held laser scanner at a specified distance from an object bearing a bar code symbol, the presence of the object is automatically detected using an infrared (IR) light beam or a low-power laser light beam, the presence of the bar code symbol on the object is detected using a visible laser light beam, and thereafter the detected bar code symbol is automatically scanned and decoded (i.e. read) to produce symbol character data representative of the read bar code symbol. Prior art illustrative of this second category of laser-based bar code symbol reading systems are disclosed in the following patents: U.S. Pat. Nos. 4,639,606; 4,933,538; 5,828,048; 5,828,049; 5,825,012; 5,808,285; 5,796,091; 5,789,730; 5,789,731; 5,777,315; 5,767,501; 5,736,982; 5,742,043; 5,528,024; 5,525,789; D-385,265; 5,484,992; 5,661,292; 5,637,852; 5,468,951; 5,627,359; 5,424,525; 5,616,908; 5,591,953; 5,340,971; 5,340,973; 5,557,093; 5,260,553; and EP-A-0871138.
Automatically-activated laser scanning bar code symbol readers of the type disclosed in the above-referenced US Letters Patents enable the reading of bar code symbols without the shortcomings and drawbacks of manually-activated hand-held bar code symbol readers. However, automatically-activated bar code symbol readers can at times aggressively read bar code symbols that are not desired to be read by the user as, for example, when attempting to read a particular bar code from a list of bar code symbols closely printed on a bar code menu or like structure. This is caused by the laser scanline within the scanning field scanning across two or more bar code symbols at the same time, which is likely to occur when the bar code scanner is positioned at a large distance from the object and the laser scanline is large due to the scanning geometry of the scanner. Oftentimes inadvertent bar code symbol reading errors must be corrected at their time of occurrence, wasting valuable time and resources of the user.
Notably, the use of the short-range CCD-emulsion mode taught in U.S. Pat. No. 5,558,024 provides a solution to the problem of inadvertently reading undesired bar code symbols closely printed on bar code menus. However, even when using this short-range CCD emulation mode, it is possible for the automatically-generated laser scanning pattern to inadvertently read an undesired bar code from the bar code menu as the operator moves the head portion of the hand-held reader into position over the bar code symbol to be read. This is due to the width of the laser scanning plane intersecting the object plane bearing the bar code symbol to be read. While it is possible in theory to operate the IR-based object detector in a short-range mode of operation, cost considerations make this difficult to achieve in practice.
Also, in order to enjoy the benefits of the short-range CCD-emulation mode, the laser scanning bar code symbol reader must be induced into this mode of operation either by reading a presignated (function-programming) bar code symbol, or by manually actuating a switch on the exterior of the scanner housing. Then, after reading the bar code symbol from the menu while the device is in its short-range CCD-emulation mode, the user is required to reconfigure the scanner back into its long-range mode of operation so that it can be used to read bar codes within a large depth of field of the reader. Until steps are taken to reconfigure the bar code symbol reader into its long range mode of operation, the user is forced to read bar code symbols in its CCD-emulsion mode which can be inconvenient in many types of scanning applications, thus reducing worker productivity.
When using the above-described system to read bar code symbols on products that have been placed among a set of previously “scanned” products at a check-out counter, there is a high likelihood that previously scanned products will be accidentally re-read, creating an error in check-out operations. Notably, the structure of this problem is quite similar to the bar code menu reading problem described above.
In wireless portable bar code symbol reading apparatus, the above problems are further exacerbated because of the need of the consumer battery power.
Thus, there is a great need in the art for an improved system and method of reading bar code symbols using automatically-activated laser scanning mechanisms while overcoming the above described shortcomings and drawbacks of prior art systems and methods.